1. Field of the Invention
The instant invention relates generally to processes for preparing a polyester copolymer resin and more specifically it relates to a process for dispersing a crude polyester copolymer resin and separating out, via continuous multi-stage filtration, the smallest size particles present in the crude starting material.
2. Description of the Prior Art
It is known in the art to utilize filter systems to separate polyester copolymer resin dispersions. Speaking generally, these methods use inert filter aides such as diatomaceous earth. The most common filter press design consists of alternate plates and frames hung on a rack and forced tightly together with a hydraulic closing mechanism. Feed slurry is then pumped to the press under pressure. As the filtration proceeds, filter cakes build up on the filter cloths until the cakes form a nearly solid mass, requiring that they be removed for further processing. With these processes, the finished product (the polyester resin) is obtained in the form of the filter cake removed from the filter press, and the filtrate solution is the by-product. In the instant invention, however, the filtrate is the desired product and the removed sediment is the by-product.